The present invention relates generally to self-assembly, and more particularly to surface-selective self-assembly of component articles, including those spanning the micron to centimeter range and optionally including electronic circuitry, into composite articles.
Self-assembly is a term used to define the spontaneous association of entities into structural aggregates. The best-known and most well-researched area of self-assembly involves molecular self-assembly, that is, the spontaneous association of molecules, a successful strategy for the generation of large, structured molecular aggregates. Self-assembly of molecules in solution is described by Whitesides, et al., in xe2x80x9cNoncovalent Synthesis: Using Physical-organic Chemistry to Make Aggregatesxe2x80x9d, Accts. Chem. Res., 28, 37-44 (1995). See also Philp, et al., Angew. Chem., Int. Ed. Engl., 35, 1155-1196 (1996) for molecular self-assembly. Nature includes examples of molecular self-assembly where, in the field of biology, many processes involve interfacial interactions and shape selectivity to form complex, three-dimensional structures.
Self-assembly of molecules can be made to occur spontaneously at a liquid/solid interface to form a self-assembled monolayer of the molecules when the molecules have a shape that facilitates ordered stacking in the plane of the interface and each includes a chemical functionality that adheres to the surface or in another way promotes arrangement of the molecules with the functionality positioned adjacent the surface. U.S. Pat. No. 5,512 131, and U.S. patent application Ser. Nos. 08/695,537, 08/616,929, 08/676,951, and 08/677,309, and International Patent Publication No. WO 96/29629, all commonly-owned, describe a variety of techniques for arranging patterns of self-assembled monolayers at surfaces for a variety of purposes. See also Whitesides, G. M., xe2x80x9cSelf-Assembling Materialsxe2x80x9d, Scientific American, 273, 146-149 (1995) for a discussion of self-assembly.
Self-assembly of components larger than molecules is known, for example, self-assembly of bubbles at an air-liquid interface, small spheres self-assembled on surfaces, self-assembly of microspheres via biochemical attraction between the microspheres, and the like. In xe2x80x9cA DNA-Based Method for Rationally Assembling Nanoparticles Into Macroscopic Materialsxe2x80x9d, Nature, 382, (Aug. 15, 1996), Mirkin, et al., describe a technique for assembling colloidal gold nanoparticles, reversibly, into macroscopic aggregates. Non-complementary DNA oligonucleotides capped with thiol groups that bind to gold are attached to the surface of batches of 13 nm gold particles. When the particles are placed into a solution to which is added an oligonucleotide duplex with xe2x80x9csticky endsxe2x80x9d complementary to the two grafted sequences, the nanoparticles self-assemble into aggregates. The assembly can be reversed by thermal denaturation. Yamaki, et al., in xe2x80x9cSize Dependent Separation of Colloidal Particles in Two-Dimensional Convective Self-Assemblyxe2x80x9d Langmuir, 11, 2975-2978 (1995), report xe2x80x9cconvective self-assemblyxe2x80x9d of colloidal particles ranging in size from 12 nm to 144 nm in diameter in a wetting liquid film on a mercury surface. Size-dependent two-dimensional convective assembly occurred, with larger particles being positioned in the center of the aggregate and smaller particles at the periphery. Cralchevski, et al., in xe2x80x9cCapillary Forces Between Colloidal Particlesxe2x80x9d Langmuir, 10, 23-36 (1994), describe capillary interactions occurring between particles protruding from a liquid film due to the capillary rise of liquid along the surface of each particle. A theoretical treatment of capillary forces active spheres is presented. Simpson, et al., in xe2x80x9cBubble Raft Model for an Amorphous Alloyxe2x80x9d, Nature, 237-322 (Jun. 9, 1972), describe preparation of a two-dimensional amorphous array of bubbles of two different sizes as a model of an amorphous metal alloy. The bubbles were held together by a general capillary attraction representative of the binding force of free electrons in the metal.
U.S. Pat. No. 5,45,291 (Smith) describes assembly of solid microstructures in an ordered manner onto a substrate through fluid transfer. The microstructures are shaped blocks that, when transferred in a fluid slurry poured onto the top surface of a substrate having recessed regions that match the shapes of the blocks, insert into the recessed regions via gravity. U.S. Pat. No. 5,355,577 (Cohn) describes a method of assembling discrete microelectronic or micro-mechanical devices by positioning the devices on a template, vibrating the template and causing the devices to move into apertures. The shape of each aperture determines the number, orientation, and type of device that it traps.
While self-assembly at the molecular level is relatively well-developed, self-assembly at larger scales is not so well-developed. Many systems in science and technology require the assembly of components that are larger than molecules into assemblies, for example, microelectronic and microelectrochemical systems, sensors, and microanalytical and microsynthetic devices. Photolithography has been the principal technique used to make microstructures. Although enormously powerful, photolithography cannot easily be used to form non-planar and three-dimensional structures, it generates structures that are metastable, and it can be used only with a limited set of materials. Accordingly, it is an object of the present invention to provide techniques for the rational self-assembly of component articles into composite structures according to predetermined arrangements.
The present invention provides techniques for self-assembly of component articles. In one aspect, the invention provides a method of self-assembly including providing a first component article having a maximum dimension, a total surface area, and a first mating surface. A second component article is provided that also has a maximum dimension, a total surface area, and a second mating surface that matches the first mating surface of the first component article. The first and second mating surfaces each define an area equal to at least 1% of the lesser of the total surface areas of the first and second component articles. Preferably, the first and second mating surfaces each define an area equal to at least 5% of the lesser of the total surface areas of the first and second component articles, more preferably at least 10%. The first and second component articles are separated by a distance at least equal to {fraction (1/100)} of the maximum dimension of the first or second component article, preferably separated by a distance at least equal to {fraction (1/50)} the maximum dimension, preferably at least {fraction (1/25)}, and more preferably still a distance at least equal to the maximum dimension. Then, without applying a net external force to either of the first and second component articles, and under set conditions, the first mating surface is allowed to fasten to the second mating surface in a manner that is irreversible under the set conditions. A composite article of the first and second component articles is thereby formed. In another embodiment the method involves allowing the first and second mating surfaces to mate in the presence of a net external force. A third component article can be added to the system and the method can involve allowing a mating surface of the third article to fasten to the mating surface of the second component, irreversibly under the set conditions.
According to another embodiment the invention involves a method of self-assembly that includes first and second component articles each including a total surface area, a first mating surface, and a remainder surface. The first and second mating surfaces each are compatible with the other and are incompatible with the remainder surfaces. Without applying a net external force to either of the first and second component articles, and under set conditions, the first mating surface is allowed to fasten to the second mating surface irreversibly under the set conditions.
In another embodiment, the invention provides a method of self-assembly in which first and second component articles are provided each having a dimension of at least 150 nm, a total surface area, and a mating surface. The mating surfaces of the respective component articles match, and each define an area equal to at least 1% of the lesser of the total surface areas of the first and second component articles. Without applying a net external force to either of the first and second component articles, the first and second mating surfaces are allowed to fasten to each other. A composite article is formed thereby via connection of the first and second mating surfaces.
According to another aspect of the invention a self-assembled article is provided. The article is a self-assembled composite of a plurality of separate component articles joined at respective matching mating surfaces. The component articles each have a dimension of at least 150 nm.
According to yet another aspect an electrical circuit is provided in the invention. The electrical circuit comprises a self-assembled composite of a plurality of separate component circuit articles that are joined at respective matching mating surfaces. A plurality of the separate component circuit articles each include an electrical conductor in electrical communication with an electrical conductor of an adjacent component article in the circuit to which it is fastened via self-assembly.
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure.